Final answer:
The knife blade should generally face away from the body for safety, for a wire on the y-axis with current in +y-direction, the magnetic field on the +x-axis is out of the page, and for a downward magnetic field, current should flow from right to left for a rearward-pointing force.
Step-by-step explanation:
The question seems to be focused on understanding the direction of effects in different contexts, such as the cutting of a knife blade, the orientation of the body, the magnetic field around a wire, and the flow of current in relation to a magnetic field. When it comes to safety and usage of a knife, the blade should generally face away from the body to minimize the risk of injury. In terms of the magnetic field created by a current-carrying wire, according to the right-hand rule, for a wire carrying current in the positive y-direction, the magnetic field at a point on the positive x-axis would be directed out of the page.
Lastly, if the magnetic field is downward and we want a rearward-pointing force, using the right-hand rule for a wire, we can determine that the current must flow horizontally from right to left when viewed from the rear of the boat.